BACKGROUND: Deep vein thrombosis (DVT) is a common complication following major surgical procedure. In regional anesthesia with local anesthetics, deep vein thrombosis is less frequent than in general anesthesia. Several studies have advocated that local anesthetics alter the function of platelets, the stability of vascular endothelium, and the hemodynamics of the blood flow in the epidural anesthetic region. We investigate the effect of the local anesthetic bupivacaine on blood coagulation in vitro under thromboelastography (TEG). METHODS: 16 Healthy volunteers who had no history of coagulation defect and anticoagulant use were evaluated. The patients were divided into 4 groups and each group was treated with bupivacaine in the following concentrations; the lower clinical level (1 microgram/ml, B1 group), the higher clinical level (2 microgram/ml, B2 group), the systemic toxicity level (4 microgram/ml, B3 group), and a control group which was treated with normal saline. We compared the TEG parameters of each group, reaction time (R), coagulation time (K), alpha angle (alpha), maximal amplitude(MA) and fibrinolysis index (lysis 60), respectively. RESULTS: As compared with the control group, there were no significant differences in the other 3 groups, especially in maximal amplitude. CONCLUSIONS: In the clinical concentration, bupivacaine had no effect on blood coagulation under TEG. Thus in the clinical concentration of bupivacaine, DVT is more influenced by several physiologic changes which are induced by epidural anesthesia, include stability of vascular endothelium, increased blood flow, and decreased catecholamine release rather than by the effect of bupivacaine on blood per se.